The delivery of an exogenous genetic element to cells and tissues in vivo has the potential to alter either their phenotype or pattern of differentiation if the DNA is transcribed and translated to produce a functional protein. In addition if this protein is secreted from the cells its circulation throughout the organism could result in a systemic effect due to the newly introduced DNA. Several different techniques have been developed to introduce new genetic sequences into cells, each having a particular set of strengths and weaknesses. procedures have been developed in our laboratory to inject naked plasmid DNA directly into tongue muscle such that the expression of the gene encoded by the DNA occurs. The tongue muscle presents several advantages for the delivery of new genes; including ready accessibility, non-proliferative cell population, high vascular flow, and uniform dense striated muscle, which have been used to advantage in the techniques developed in our laboratory. The method that has been developed has resulted in expression of reporter genes at the site of injection, and delivery of expressed proteins into the circulation for a systemic effect. The present studies are proposed to further develop this system and determine the applicability of inducible promoters and the time course for gene expression. The hypothesis for this project is; DNA expression plasmids directly injected into tongue muscle can be regulated through the use of inducible promoters. This hypothesis will be tested with two specific aims; 1) To determine whether inducible promoters included in a DNA expression plasmid will permit control of the temporal and quantitative patterns of expression of the reporter gene following injection into tongue muscle, 2) To determine whether the injected DNA plasmids will persist in the tongue muscle for extended periods and permit periodic or delayed induction and subsequent expression of the reporter gene. The longterm goal of this research is to develop the tongue injection model as a system suitable for gene therapy.